The simplest explanation of such universality of the production kinematics is that
one and the same parton-level process (or mixture of processes)
describes the production of all states, irrespectively of their masses and quantum numbers.
In fact, the kinematic dependence of the partonic cross section of a given process is invariant
by simultaneous rescaling of all energy-related variables.
This translates to an invariance by \(p_{\rm T}/M\)  rescaling,
if the longitudinal momentum components can be neglected:
such scaling is not expected to be valid in the low \(p_{\rm T}/M\)  and high-rapidity
region of the LHCb
data (see Refs. [1]}, [2]}, [3]} and references therein).
On the other hand, as shown in Ref. [4]},
current fixed-order perturbative calculations are seemingly unsuitable
to describe cross section measurements for \(p_{\rm T}/M \lesssim 3\) ,
justifying that relatively high-\(p_{\rm T}\)  data remain preferable in data-theory comparisons.
